Network Basics: Ethernet Configurations - dummies

Network Basics: Ethernet Configurations

Ethernet has a variety of possible configurations, standard, fast and gigabit. Each version operates at different speeds and use different types of media. All the versions of Ethernet are compatible with each other, so you can mix and match them on the same network by using devices such as bridges, hubs, and switches to link network segments that use different types of media.

Standard Ethernet

Standard Ethernet is the original Ethernet and the slowest. It runs at 10 Mbps, which was considered fast in the 1970s but is now considered slow and obsolete.

Standard Ethernet comes in four incarnations, depending on the type of cable used to string the network together:

  • 10Base5: The original Ethernet cable was thick (about as thick as your thumb), heavy, and difficult to work with. It’s seen today only in museums.

  • 10Base2: This thinner type of coaxial cable (it resembles television cable) became popular in the 1980s and lingered into the early 1990s. Plenty of 10Base2 cable is still in use, but it’s rarely installed in new networks. 10Base2 (like 10Base5) uses a bus topology.

  • 10BaseT: Unshielded twisted-pair cable (known as UTP) became popular in the 1990s because it’s easier to install, lighter, and more reliable, and it offers more flexibility in how networks are designed. 10BaseT networks use a star topology with hubs at the center of each star. Although the maximum length of 10BaseT cable is only 100 meters, hubs can be chained together to extend networks well beyond the 100-meter limit.

    10BaseT cable has four pairs of wires that are twisted together throughout the entire span of the cable. However, 10BaseT uses only two of these wire pairs, so the unused pairs are spares.

  • 10BaseFL: Fiber-optic cables were originally supported at 10 Mbps by the 10BaseFL standard. However, because faster fiber-optic versions of Ethernet now exist, 10BaseFL is rarely used.

Fast Ethernet

Fast Ethernet refers to Ethernet that runs at 100 Mbps, which is ten times the speed of Standard Ethernet. The following are the three varieties of Fast Ethernet:

  • 100BaseT4: The 100BaseT4 protocol allows transmission speeds of 100 Mbps over the same UTP cable as 10BaseT networks. To do this, it uses all four pairs of wire in the cable. 100BaseT4 simplifies the task of upgrading an existing 10BaseT network to 100 Mbps.

  • 100BaseTX: The most commonly used standard for office networks today is 100BaseTX, which transmits at 100 Mbps over just two pairs of a higher grade of UTP cable than the cable used by 10BaseT. Most new networks are wired with the higher-grade cable, Category 5, or better cable.

  • 100BaseFX: The fiber-optic version of Ethernet running at 100 Mbps is called 100BaseFX. Because fiber-optic cable is expensive and tricky to install, it isn’t used much for individual computers. However, it’s commonly used as a network backbone.

Gigabit Ethernet

Gigabit Ethernet is Ethernet running at a whopping 1,000 Mbps, which is 100 times faster than the original 10 Mbps Ethernet. Gigabit Ethernet was once considerably more expensive than Fast Ethernet, so it was used only when the improved performance justified the extra cost. However, today Gigabit Ethernet is the standard for nearly all desktop and laptop PCs.

Gigabit Ethernet comes in two flavors:

  • 1000BaseT: Gigabit Ethernet can run on Category 5 UTP cable, but higher grades such as Category 5e or Category 6 are preferred because they’re more reliable.

  • 1000BaseLX: Several varieties of fiber cable are used with Gigabit Ethernet, but the most popular is called 1000BaseLX.